Switching device controllable by a light source



April 5, 1960 D. J. H- ADMIRAAL EI'AL Y 2,931,944 swncumc DEVICE CONTROLLABLE BY A LIGHT souRcE Filed Nov. 29, 1957 FIGJ FIG.2

VE NTOR DANIEL JOHANNES HINDERIQUS ADMIRAAL ADRIMN JULIUS VAN DER HOUVEN VAN ORDT AGENT .in French Patent Nos. 1,035,492 and 1,071,113.

nited States SWITCHING DEVICE CONTROLLABLE BY A LIGHT SOURCE Application November 29, 1957, Serial No. 699,675

Claims priority, application Germany December 2-1, 1956 17 Claims. (Cl. 315-83) This invention relates to switching devices controllable by a light source and intended more particularly for automatically dimming the headlights of a car, when the light source moves in a determined direction towards and past the switching device and radiates light in the direction of its movement.

Such switching devices have previously been described The last-mentioned patent relates to an improved construction of a known form of such devices. However, the switching device according to said patent is adapted to American conditions and has the disadvantage that, if an on coming car dims its headlights first, the headlights of the vehicle equipped with the switching device are dimmed much too late. That is, the lights are dimmed only when the dimmed headlights of the oncoming car, as a result of the decreased distance, have become sufficiently strong to render the switching device operative.

In one known arrangement, the headlights'of vehicles are dimmed merely by decreasing theamount of light, so that according to European'conceptions the amount of light radiated forwards and horizontally is still too large.

In another known arrangement, the amount of light radiated is usually not decreased to a considerable extent,

but the radiation of the headlights is directed downwards, so that the road is even better illuminated at a short distance in front of the vehicle, but the light beams cannot directly strike the eyes of the driver of an oncoming car. 1

These conditions are shown diagrammatically in Figures 1 and 2 of the accompanying drawing. (headlight above and dimlight below).

In a well known form, the switching a very sensitive, forwards directed photo-electric cell with multiplier, and an amplifier controlling a relay. When the headlights of the vehicle comprising this device are dimmed, the relay. closes an additional contact, resulting in the amplification of the amplifier and the, sensitivity of the device being increased to an extentsuch that, upon dimming of the headlights of the. oncoming car, the device remains in the dimlight position until the vehicle has finally passed. In order to accurately guarantee switching over to headlight, the sensitivity of atent O .device comprises the device is gradually reduced. with a suitably chosen electric time-constant.

If dimming is effected according to the above first dimming is effected in accordance with the above sec ond described system, such switching devices are not operative at all or are operated only at a very small distance of an oncoming car in the second case.

, ...Th .=.v. t. i s i s a r EW QhPM N 2,931344' Patented Apr. 5, 1960 2 1,035,492 is not adapted for the above-noted beam lowering systems.

In thisdevice, the switching over to dimlight is intentionally delayed, whichmay have the result that it does not switch over again to headlight if the headlights ofthe oncoming car are dimmed in their turn. Switching over to head-light is brought about by a light pulse which is thrown via a mirror onto the photo-electric cell by a spotlight arranged especially at the back of the passing vehicle and radiating light laterally against the vehicle comprising the switching device. A condition for this automatic switch-over to headlight is thus the standardized equipment of all motor vehicles with an addition spotlight, hitherto unusual and radiating sideways. i e

g In the switching device according to the present invention, switching-over is efiected by action of the light from the headlights of a passing vehicle upon a second photo-electric cell, which light, as shown in Figures 3 and 4, is radiated directly to the side, that is not concentrated into a beam. With ordinary photo-electric cells, a complicated amplifying equipment is thus required and the device is therefore a little more complicated and more expensive than switching devices of known type. When using very sensitive photo-electric cells, more particularly photo-conducting cells, for example .cells of cadmium sulphide with activating additions, this equipment becomes much cheaper and simpler since the whole-amplifying equipment together with a direct voltage converter for thesupply thereof may be dispensed with.

The switching device according to the present invention comprises by a first light-sensitive cell arranged to be illuminated by the light source when still fairly remote, a second light-sensitive cell arranged 'to be temporarily illuminated by the light source moving past the switching device, and a switching relay which is controlled by; the photo-cells in accordance with their respective illuminations and in a manner such that the relay assumes a first stable position when th'e first cell is illuminated and a second stable position when the second cell isilluminated andthe first cell is; not illuminated.

Due to the fact that the switching relay is stable in .either position, that is, it is held automatically in either position until. a new switching command is received, the .dimming vof the headlights of a vehicle movingtowards the switching device cannot bring about premature switching over. Pheferably, means are even provided'by which the switching relay is also brought into its first position byan, abrupt strong decrease of the illumination of the first cell, so that, if the headlights of a vehicle moving towards .the switching device are dimmed, before the switching relay has assumed its first position, this dimming causes the switching relay to be switchedover to its first position. The accompanying drawing illustrates the described dimming systems and the conditions of illumination when a vehicle approaches and passes and shows the circuit diagrams of three different embodiments of the switching device according to the invention.

Fig. 1 illustrates oneknown arrangement for dimming headlights; I i :qFig. 2 illustrates another known arrangement for dimming'headlights; g V Y j i 3 shows thereflected beam of rays and the direct non-concentrated:radiation, V Fig. 4is a schematic diagram of an embodiment of the switching device of'the present invention, showing the arrangement ,of the two photo-electric cells, with respect to the headlights of a vehicle moving towards and past'it;

"Fig. 5 is a schematic circuit diagram of an embodiment of the switching device of the present invention;

Fig. 6 is a schematic circuit diagram of another embodiment of the switching device of the present invention; and v v V Fig. 7 is a schematic circuit diagram of still. another embodiment of the switching device of the present invention.

In Fig. 4, a switching device according to the invention is represented diagrammatically by a rectangle 1. The main application of this device resides in the-automatic dimming of the headlights of a motor vehicle. However, it may be used for many other purposes, for example for the automatic control at night of trafiic signals at complicated and dangerous crossings which are manned in day-time. If the switching device is incorporated in a motor vehicle, it comprises a first photo-electric cell I, which is directed forwards and arranged on this vehicle so that it is illuminated, by the headlights 2 of other vehicles coming from the opposite direction. It also comprises a second photo-electric cell 11 which is directed approximately horizontally and obliquely forwards, that is, towards the side of the road on which a crossing vehicle must pass according to the traflic rules. This cell is thus ternporarily illuminated by the non-concentrated light radiated by the lamps of the headlights 2' of a vehicle passing in the opposite direction.

If the switching device is used for the automatic control of traflic signals, it may be arranged on a traffic column, for example at the center of a crossing. Let us consider, for example, the case of a crossing between motor roadsin which the road from the left to the right and conversely is a major road with respect to the other road extending from above to below and conversely (Fig. 4). The trafiic column 1 is equipped not only with the photoelectric cells I and II, but also with a second set of photoelectric cells I' and II '(shown in dotted lines). Each set of photo-electric cells supervises the main road in a given direction. When a vehicle approaches from the right hand side, the photo-electric cell I, for example, switches a switching relay into its first position and as soon as this vehicle passes the trafiic column 1, photoelectric cell II gives the command to change over to the second position. In the first position, the switching relay switches on red stoplights and in the second position yellow flicker-lights. Both the red and the yellow lights are arranged so that they are clearly visible from vehicles driving in both directions on the subordinate road, but are invisible from the'major road. The photo-electric -cells I and I and II and II may be connected in parallel, but it is preferable to utilize two switching devices hav- ,3, a second relay 4 and a comparatively sensitive auxiliary relay 5. The winding of switching relay 3 is connected at one end to a point 6 which is connected through a main switch 7, for example through the lighting switch of a motor vehicle, to the positive terminaltof a directvoltage source 8, for example, a storage battery of 12 ,volts operating voltage, At its other end, it is'connected to the negative terminal of the same source ofsupply through the photo-electric cellII and, in parallel therewith, through break contacts 41 and 51 of the relays 4 and 5 and a make contact 31. of relay 3, which is connected in series therewith and which serves as a holding contact.

The winding of the second relay 4 .is connected atone end to the point 6 and, at its other end, to the negative terminal of the source 8 via the photoelectric cell 1. The

.through its contact31.

winding of the auxiliary relay 5, in series with an electrolytic capacitor 9, bridges the same photo-electric cell, a second electrolytic capacitor 10 being connected in parallel with the photo-electric cell II.

The switching device shown in Fig. 5 comprises a third photo-electric cell III, which is incorporated in a case 12, in front of a light source, for example, a small incandescent lamp 11. The lamp 11 is connected to point 6 through a break contact 32 of relay 3 and to the negative terminalof the source 8 via the photo-electric cell I. The photo-eiectric cell III is connected in parallel with the cell II. A push-button switch 13, for example, a footoperated switch, is provided, by means of which the photo-electric cells I and II, and III respectively, may be alternately short-circuited for a short period. Finally, the switching relay 3 comprises a make contact 33 and a break contact 34 for switching over from headlights (represented by a comparatively large incandescent lamp 14) to dimlights (small incandescent lamp 15) and conversely, and the switch 16 serves to switch otf the photoelectric cells.

When the switch 7 is closed, and the switch 16 being closed the relay 3 is first energized by the charging current of the capacitor 10 and then holds itself in its second position via contacts 41, 51 and 31, so that the headlights are switched on via contact 33. If it is desired to switch over to dimlights, the photo-electric cell I is temporarily short-circuited by means of switch 13 (righthand position). The relay 4 is thus energized, so that it opens its contact 41 and releases the relay 3, so that the dimlights are switched on via contact 34. A new push on the push-button switch 13 (left-hand position) brings -upon the concentration of the light from the headlights of the oncoming car and may be adjusted, for example, by "partial screening of the photo-electric cell I, so that the driver of the vehicle comprising the switching device is not dazzled by this light before the headlights of his car are automatically switched over.

If the driver of the oncoming car does not switch over to dimlights, the internal resistance of the photo-electric cell I decreases further until the lamp 11 fed through this .cell and back contact 32 flashes up and illuminates the photo-electric cell Ill. The internal resistance of this cell thengreatly decreases. and the relay. 3 is energized through it with a simultaneousdischarge of capacitor 10. .Due to the energization of relay 3, the headlights are .again switched over to headlights and the circuit of the .lamp 11 is interrupted. However, relay 4 is still energized through the photo-electric cell I, which is now strongly illuminated so that therelay 3 cannot hold itself The internal resistance of the cell III again increases, since it isno longerilluminated,

.and the relay 3 is released. The. switching device thus .automatically produces flicker-light signals with the headlights at ,a frequency which increases with the intensity of illumination of the cell I and until the headlights of the oncoming car are dimmed.

. .If,the hcadlightsof theoncoining car are. dimmed bethis abrupttdimming causes a suddenincrease of the. in-

fcreithose of the vehicle comprising the switching device,

switches over to dimlightsi gized through this cell and if the cell'I'is' not illuminated,

or only weakly illuminated at this time, said relay i's'energized and holds itself again in the headlights position through its contact 31.

Instead of utilizing a photo-electric cell III connected in parallel with the photo-electric cell II, it is alternatively possible to arrange the lamp 11 so that its light strikes the photo-electric cell II, for example, by reflection thereon by means of a transparent mirror. The capacitor 10 prevents too rapid an increase in. voltage at the terminals of the winding'of relay 3 and. hence unwanted switching over to headlights underthe action oiilight from interfering light sources, for example, of the concentrated light from comparatively distant light sources.

Due to the provision of the auxiliary relay 5 and of the capacitor 9, the switching device is sensitive not only to a determined light intensity, but also to rapid variations in light intensity.

The embodiment shown in Fig. 6 resembles that of Fig. 5, corresponding parts of these switching devices and also of the switching device shown in Fig. I being provided with the same reference numerals; V

In the embodiment shown in Fig. 6, the relay com prises a second winding 3' having a comparativelylarge number of turns. In-the energized, position, the relay 3 holds itself via its contact 31 and a resistor 17, thevalue of which may be higher than that of the internal resistance of the photo-electric cell II in theilluminated condi- ;tion. The cellI shunts the mainwinding of relay 3, the resistance of which in turn is higher than that of the illuminated cell I, so that the relay 3 is deenergized upon sufiiciently intense illumination of the photo-electric cell I. When the headlights of an oncomingcar are dimmed first, the capacitor 9discharges through the auxiliary winding 3' and the main winding of relay 3. Furthermore, the current traversing the main winding of the relay 3 and the resistor 17 increases; However, the respective numbers of turns of the main winding and of the auxiliary winding and the value of capacitor 9 may be so chosen that the effect of the current traversing the auxiliary winding, which counteracts the current traversing the main winding, is temporarily predominant'and causes the relay 3 to be deenergized. When the'photo-electric cell II is illuminated while cell I is not, the main winding of relay 3 is energized through cell'II.

With respect to the embodiment shown in Fig. 5, in that shown in Fig. 6, two relays (4 andS') ar'e dispensed with at the price of a more expensive relay 3 provided with two windings. A flicker-light signal device comprising photo-electric cell III and lamp 11 is not shown in Figs. 6 or 7, but could be added in exactly the same manner to the embodiments of these figures as well.

In the embodiment shown inFig. 7', the photoelectric cells I and II control a'trarisistor change-over switch, which in turn switches the current through the winding of switching relay 3. The'change-overv switch shown-is of the type described in c'opending US. application Serial No. 564,068, filed Feb. 7, 1956. It comprises two tran sisters 18 and 19 of opposite conductivity types, the emitters of which are connected together and the collectoremitter paths of which are connected in series with each other and with a load (winding of'relay. 3). By way of the switch 16, the photo-electric cells I and II are shunted by resistors 20 and 21 of a potentiometer included between the collectors of the two transistors, the tapping point'on the potentiometer being connected to the movable I contactof push button switch 13 andto the base of transisto'r-18.. The base of transistor-l9 is connected to the d tapping point of another potentiometer comprising resistors 22 and'23 and connected between point 6iand the negative terminal of the source 8., Furthermore, the bases of the two transistors are connected together via capacitor 9.

Whenthe internal resistance of cell II decreases, or when the switch 13 is temporarily moved to its left-hand position, the base of transistor lflbecomes positive with respect to its emitter. This transistor becomes conducting, so that the emitter of transistor 19 becomes positive with respect to its base. Both transistors are then conducting and a considerable current flows through the winding of relay 3, which is energized and switches over to headlights. The voltage drop across the winding of relay 3 holds the transistor 18 and hence also the transistor 19 in the conducting state. v

When the internal resistance of the photo-electric cell I greatly decreases, or when the switch 13 is temporarily moved to its right-hand position, the base of transistor 18 becomes negative with respect to its emitter and the circuit via the two transistors is cut off, so that the relay 3 is deenergized and switches over to dimlights. When the internal resistance of the cell I first decreases and then abruptly increases (premature dimming of the headlights of an oncoming car), a positive pulse reaches the base of transistor 18. This pulse would tend to open transistor 18 still further. However, via capacitor 9 and after ditferentiation and sharpening by the RC-members 9, 22, 23, it reaches the base of transistor 19 and cuts off this transistor, resulting in the circuit via the two transistors likewise being cut-off. 1 a

The embodiments described are adapted to the needs oftrafiic and thesatisfactory operation thereof is by no means dependant on any standardized modification in the equipment of existing vehicles- Theymay be used with both dimming systems above described. I

While the invention has been described by means of light source, comprising a first light sensitive cell positioned in a manner whereby it is illuminated by said light source from a relatively large distance to relative proximity between said first cell and the said light source, a second light sensitive cell positioned in a manner whereby it is illuminated by said light source when-the said light source reachesa point beyond the area wherein said first cell is illuminated by the said light source, a switching relay comprising a switching member having at least two stable positions and means for controlling the positioning of said switching member, and meanscoupling said first and second cells to said switching member control means in a manner whereby the said switching mem her is positioned in a first stable position when said first cell is illuminated andthe said switching member is positioned in a second stable .positionwhen said second cell is illuminated.

2. A switching device controlled by a headlight on an approaching vehicle, comprising a-first light sensitive cell positioned in a manner whereby it is illuminated by said headlight from a relatively large distance to relative proximity between said first cell and the said headlight, a second light sensitive cellpositioned in a manner whereby it i is illuminated by said headlight when the said headlight reaches a point beyond the area wherein said first 'cell is approaching vehicle, comprising a first light sensitive cell positioned in a manner whereby it is illuminated by said headlight from a relatively large distance to relative proximity between saidfirst cell and the saidheadlight, a second light sensitive cell positioned obliquely to said first cell in a manner wherebyit is illuminated'by said headlight when the said headlight reaches a point beyond the area wherein said first cellis illuminated by the said headlight, a switching relay comprising a switching member having a first stable position, a second stable position and 'means'for controlling the positioning of said switching member, a first light control circuit including said switching member in said first stable positioma second light control circuit including said switching member in said second stable position, and means coupling said first and second cells to said switching member control means in a r manner whereby the said switching member is positioned in said first stable position thereby closing said first light control circuit when said first cell is illuminated and the said switching member is positioned in said second stable position thereby closing said second light control circuit when said second cell is illuminated. I V I d 4. A switching device controlled by an approachin light source, comprisinga first light sensitive cell positioned in a manner whereby it is illuminated by said light source from a relatively large distance to relative proximity between said first cell and the said light source, a second light sensitive cell positioned in a manner whereby it is illuminated by said light source when the said light source reaches a point beyond the area wherein said first cell is illuminated by the said light source, a switching relay comprising a switching member having at least two stable positions and means for-controlling the positioning of said switching member, said switching member control means comprising means including one of said cells for energizing said switching member when said one of the said cells is illuminated and means including the other of said cells for holding the said switching member in position, saidiholding means being inoperative when said other of the said cells is illuminated, and means coupling said first and second cells to said switching member consecond light sensitive cell of high sensitivity positioned in a manner whereby it is illuminated by said light source when the said light source reaches a point beyond the area wherein said first cell is illuminated by the said light source, a switching relay comprising a switching member having at. least two stable positions and means for controlling the positioning of said switching member, said switching member control means comprising means including said second cellfor directly energizing said switching member when the said second cell is illuminated, and means coupling said first andvsecond cells to said switchmg membercontrol means .in a manner whereby thesaid switching member is positionedina first stableposition when, said first cell isiIIun-linated and. thesaid switching member is positioned ginma second stable position when said secondcell is illuminated.

lillum inated and the said switching member is positioned in a second stable position when said second cell is illumia a 8 6..A switching device controlled by an approaching light source, comprisinga first light sensitive cell positioned in a manner whereby it is illuminated by said light source from arelatively large distance to relative proximity between said first cell and the said light source, a second lightsensitivetc'ell positioned in a manner whereby it is illuminated by said light source when the said light source reaches a point beyond the area wherein said first 'cell' is illuminated'by the said light source, a switching relay comprising a switching member having at least two of said switching member, said switching member control means comprising means including one of said cells for energizing said switching member when said one of the said cells is illuminated and meanslfor holding the said switching member in-position, said holding means comprising an auxiliary relay, an energizing circuit for said auxiliary relay, said energizing circuit including the other of said cells, and contact means controlled bysaid auxiliary relay for holding said switching member, said holding means being inoperative when said other of the said cells is illuminated, and means coupling said first and second cells to said switching member control means in a manner whereby the said switching member is positioned in a first stableposition when said first cell is nated.

7. A switching device controlled by an approaching light source,comprising a first light sensitive cell positioned in a manner whereby it is illuminated by said light relay comprising a switching member having at least two stable positions and means for controlling the positioning of said switching member, said switching member control means comprising means including said second cell for energizing said switching member when the said second cell is illuminated and means for holding the said switching member'in position, said holding means comprisingan auxiliary relay, an anergizing circuit for said auxiliary relay, said energizing circuit including said first cell, and contact means controlled by said auxiliary relay for holding said switching member, said holding means being inoperative whensaid first cell is illuminated, and means coupling said first and second cells to said switching member control means in a manner whereby the said switching member is positioned in a first stable position when said first cell is illuminated and the said switching 'member is positioned in a' secondstable position when 55" {said headlight from a relatively large distance to relative proximity between said first cell and the said headlight, a second light sensitive cell positioned on said automovtive vehicle in a manner. whereby it is illuminated by said headlight, a switching relay comprising a switching said switching member, a dimlight circuit for said autov. first stable position, said switching .membercontrol means motive vehicle includingsaid switching member in said 1 comprising means for positioning saidswitching member in said first stableposition thereby closing said dimlight circuit when saidfirst cell is. initially illuminated and said illumination is abruptly decreased in intensity whereby said switching member is positioned in said first stable position when said headlight of said approaching vehicle is dimmed, a headlight circuit for said automotive vehicle including said switching member in said second stable position, and means coupling said first and second cells to said switching member control means in a manner whereby the said switching member is positioned in said first stable position thereby closing said dimlight circuit when said first cell is illuminated and the said switching member is positioned in said second stable position thereby closing said headlight circuit when said second cell is illuminated.

9. A switching device for an automotive vehicle controlled by a headlight on an approaching vehicle, comprising a first light sensitive cell positioned on said automotive vehicle in a manner whereby it is illuminated by said headlight from a relatively large distance to relative proximity between said first cell and the said headlight, a second light sensitive cell positioned on said automotive vehicle in a manner whereby it is illuminated by said headlight when the said headlight reaches a point beyond the area wherein said first cell is illuminated by the said headlight,'a switching relay comprising a switching member having a first stable position, a second stable position and means for controlling the positioning of said switching 1nember, a dimlight circuit for said automotive vehicle including said switching member in said first stable position, said switching member control. means comprising an auxiliary relay winding for controlling the positioning of said switching member, a capacitor connected in series circuit arrangement with said auxiliary relay winding for energizing the said winding and means connecting said series circuit arrangement across said first cell whereby when said first cell is initially illuminated and said illumination is abruptly decreased in intensity said winding is energized and said switching member is postioned in said first stable position thereby closing said dimlight circuit when said headlight of said approaching vehicle is dimmed, a headlight circuit for said automotive vehicle including said switching member in said second stable position, and means coupling said first and second cells to said switching member control means in a manner whereby the said switching member is positioned in said first stable position thereby closing said dimlight circuit when said first cell is illuminated and the said switching member is positioned in said second stable position thereby closing said headlight circuit when said second cell is illuminated. Y

10. A switching device controlled by a headlight on an approaching vehicle, comprising a first light sensitive cell positioned in a manner whereby it is illuminated by said headlight from a relatively large distance to relative proximity between said first cell and the said headlight, a second light sensitive cell positioned in a manner whereby it is illuminated by said headlight when the said headlight reaches a point beyond the area wherein said first cell is illuminated by the said headlight, a third light sensitive cell, means for illuminating said third cell, ,a switching relay;comprising a switching member having a first stable position, a second stable position and means for controlling the positioning of said switching member,

. a first light control circuit including said switching member in said first stable position, said illuminating means and means connecting the said illuminating means in said first light control circuit in a manner whereby the saidilluminating means is energized when the said first light control circuit is closed andsaid first cell is relatively intensely illuminated, a second light control circuit including said switching member in said second stable position, and means coupling said first, second and third cells to said switching member control means'in a manner whereby the said switching member is positioned in said first stable position thereby closing said first light control circuit when said first cell is illuminated and the said switching member is positioned in said second stable light sensitive cell connected in parallel circuit arrangement with said second cell, means for illuminating said third cell, a switching relay comprising a switching member having a first stable position, a second stable position, a break contact and means for controlling the positioning of said switching member, a first light control circuit including said switching member in said first stable position, said illuminating means and means connecting the said illuminating means in said first light control circuit with said first cell and said break contact in a manner whereby the said illuminating means is energized when the said first light control circuit is closed and said first cell is relatively intensely illuminated, a second light control circuit including said switching member in said second stable position, and means coupling said first, second and third cells to said switching member control means in a manner whereby the said switching member is positioned in said first stable position thereby closing said first light control circuit when said first cell is illuminated and the said switching member is positioned in said second stable position thereby closing said second light control circuit when said second cell is illuminated and when said third cell is illuminated. 1-2, A switchingr device for an automotive vehicle controlled by a headlight o'n an approaching vehicle, comprising a first light sensitive cell positioned on said automotive vehicle in a manner whereby it is illuminated by said headlight from arelatively large distance to rela tive proximity between said first cell and the said headlight, a second light sensitive cell positioned on said .automotive vehicle in a manner whereby it is illuminated by said headlight when the said headlight reaches a point beyond the area wherein said first cell is illuminated by the said headlight, auxiliary means for illuminatingsaid second 'cell, a switching relay comprising a switching member having a first stable position, a second stable position, a break contact and means for controlling thepositioning of'said switching member, a dimlight circuit for said automotive vehicle including said switching member in said first stable position, said illuminating means and means connecting the said illuminating means in said dimlight circuit with said first cell and said break contact'in a manner whereby the said illuminating means is energized when the said dimlight circuit is closed and said first cell is relatively intensely illuminated, a headlight circuit for said automotive vehicle including said switching member in said second stable position, and means coupling said first and second cells to said switching member control means in a manner whereby the said switching member is positioned in said first stable position thereby closing said dimlight circuit when said first cell is illuminated and the said switching member is positioned in said second stable position thereby closing said headlight circuit when said second cell; is illuminated;

said first cell is illuminated by the said light source, a switching relay comprising a switching member having at least two stable positions and means for controllin'g the positioning of said switching member, said switching member control means comprising means including said second cell for energizing said switching member when the said second cell isilluminated and means forholding the said switching member in position, "said holding means comprising a winding portion of said switching relay and an energizing circuit for said winding portion, said energizing circuit including said firstcell, said holding means being inoperative when-said first cell is illuminated, and means coupling said first and second cells to said switching member control means in a manner whereby the said switching member is'p'ositioned in a first stable position when said first cell is illuminated and the said switching member is positioned in a'seco nd stable position when saidsecondcell is illuminated. I

14. A switching device controlled by an approaching light source, comprising a first light sensitivecell positioned in a manner whereby it is illuminated by said light source from a relatively large distance to relative proximity between said first cell and the said light source,

. 12 said first and second cells and said winding portion in a manner whereby said switching member is positioned in a first stablepos-ition when said first cell is illuminated and the said switching member is positioned in a a second light sensitive cell positioned in a manner whereby it is illuminated by said light source when the said winding portions and means connecting said series circuit arrangement across said first and second cells whereby when said first cell is initially illuminated and said illumination is abruptly decreased in intensity said winding portions are energized by saidcapactior and said switching member is positioned in said first stable position thereby closing said first light control circuit, a second light control circuit including s-aid switching member in a second stable position, and means coupling said first and second cells to said switching member control means ina manner whereby the said switching member is positioned in said first stable position thereby closing said first light control circuit when said first cell is illumiriated and the said switching member is positioned in said second stable position thereby closing said second light control circuit when said second 'cell is illuminated. 15. A switching device controlled by an approaching 'light source, comprising a first light sensitive cell positioned in a manner whereby it is illuminated by said light source from a relatively large distance to relative proximity between said first cell and the said light source, a second light sensitive cell positioned in a manner whereby it is illuminated by said light source when the said light source reaches a point beyond the area wherein said first cell is illuminated by the said light source,

a switching relay comprising a switching member having at least two stable positions and means forcontrolling the positioning of said switching member, said switching member control means comprising a winding portion of said switching relay for energizing said switching member when said second cell is illuminated and for holding the said switching member in position and a transistor switching arrangement, and means coupling said first and second cells to said winding portion and couplingsaid transistor switching arrangement between second stable position when said second cell is illuminated.

16. A switching device controlled by an approaching light source, comprising a first light sensitive cell positioned in a manner whereby it is illuminated by said light source from a relatively large distance to relative proximity between said first cell and the said light source, a second light sensitive cell positioned in a manner whereby it is illuminated by said light source when the said light source reaches a point beyond the area wherein said first cell is illuminated by the said light source, a switching relay comprising a switching member having at least two stable positions and means for controlling the positioning of said switching member, said switching member control means comprising a winding portion of said switching relay for energizing said switching member when said second cell is illuminated and for holding the said switching member in position and a transistor switching arrangement comprising a pair of opposite conductivity type transistors each having emitter, collector and base electrodes and a collector-emitter path, the emitter electrodes of said transistors being connected together, means connecting said collector-emitter paths in series circuit arrangement with each other and with said winding portion,

and means coupling said first and second cells to the base electrode of one of said transistors in a manner whereby .said switchingmember is positioned in a first stable position when said first cell is illuminated and the said switching member is positioned in a second stable position when said second cell is illuminated.

17. A switching device controlled by an approaching light source, comprising a first light sensitive cell positioned in a manner whereby it is illuminated by said light source from a relatively large distance .to relative proximity between said first cell and the said light source, a second light sensitive cell positioned in a manner whereby it is illuminated by said light source when the said light ing member in position and a transistor switching arrangement, said transistor switching arrangement comprising a pair of opposite conductivity type transistors each having emitter, collector and base electrodes and a collector-emitter path, the emitter electrodes of said transistors being connected together, means connecting said collector-emitter paths in series circuit arrangement with each other and with said winding portion, and a potentiometer connected across said first and second cells and between the collector electrodes of said transistors,

said first potentiometer having a tapping point connected to the base electrode of one of said transistors in a manner whereby said switching member is positioned in a first stable position when said first cell is illuminated and the said switching member is positioned in a second stable 1 position when said second cell is illuminated.

References Cited in the file of this patent UNITED STATES PATENTS 

